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<title>Metadata Proposal - ECMAScript</title>
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return function(e) {
if (opts.stopPropagation) {
e.stopPropagation();
}
var args = arguments;
if (timeout) {
clearTimeout(timeout);
}
timeout = setTimeout(function() {
timeout = null;
fn.apply(this, args);
}.bind(this), 150);
}
}
var CLAUSE_NODES = ['EMU-CLAUSE', 'EMU-INTRO', 'EMU-ANNEX'];
function findLocalReferences ($elem) {
var name = $elem.innerHTML;
var references = [];
var parentClause = $elem.parentNode;
while (parentClause && CLAUSE_NODES.indexOf(parentClause.nodeName) === -1) {
parentClause = parentClause.parentNode;
}
if(!parentClause) return;
var vars = parentClause.querySelectorAll('var');
for (var i = 0; i < vars.length; i++) {
var $var = vars[i];
if ($var.innerHTML === name) {
references.push($var);
}
}
return references;
}
function toggleFindLocalReferences($elem) {
var references = findLocalReferences($elem);
if ($elem.classList.contains('referenced')) {
references.forEach(function ($reference) {
$reference.classList.remove('referenced');
});
} else {
references.forEach(function ($reference) {
$reference.classList.add('referenced');
});
}
}
function installFindLocalReferences () {
document.addEventListener('click', function (e) {
if (e.target.nodeName === 'VAR') {
toggleFindLocalReferences(e.target);
}
});
}
document.addEventListener('DOMContentLoaded', installFindLocalReferences);
// The following license applies to the fuzzysearch function
// The MIT License (MIT)
// Copyright © 2015 Nicolas Bevacqua
// Copyright © 2016 Brian Terlson
// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
// the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
// FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
// COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
// IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
function fuzzysearch (searchString, haystack, caseInsensitive) {
var tlen = haystack.length;
var qlen = searchString.length;
var chunks = 1;
var finding = false;
var prefix = true;
if (qlen > tlen) {
return false;
}
if (qlen === tlen) {
if (searchString === haystack) {
return { caseMatch: true, chunks: 1, prefix: true };
} else if (searchString.toLowerCase() === haystack.toLowerCase()) {
return { caseMatch: false, chunks: 1, prefix: true };
} else {
return false;
}
}
outer: for (var i = 0, j = 0; i < qlen; i++) {
var nch = searchString[i];
while (j < tlen) {
var targetChar = haystack[j++];
if (targetChar === nch) {
finding = true;
continue outer;
}
if (finding) {
chunks++;
finding = false;
}
}
if (caseInsensitive) { return false }
return fuzzysearch(searchString.toLowerCase(), haystack.toLowerCase(), true);
}
return { caseMatch: !caseInsensitive, chunks: chunks, prefix: j <= qlen };
}
var Toolbox = {
init: function () {
this.$container = document.createElement('div');
this.$container.classList.add('toolbox');
this.$permalink = document.createElement('a');
this.$permalink.textContent = 'Permalink';
this.$pinLink = document.createElement('a');
this.$pinLink.textContent = 'Pin';
this.$pinLink.setAttribute('href', '#');
this.$pinLink.addEventListener('click', function (e) {
e.preventDefault();
e.stopPropagation();
menu.togglePinEntry(this.entry.id);
}.bind(this));
this.$refsLink = document.createElement('a');
this.$refsLink.setAttribute('href', '#');
this.$refsLink.addEventListener('click', function (e) {
e.preventDefault();
e.stopPropagation();
referencePane.showReferencesFor(this.entry);
}.bind(this));
this.$container.appendChild(this.$permalink);
this.$container.appendChild(this.$pinLink);
this.$container.appendChild(this.$refsLink);
document.body.appendChild(this.$container);
},
activate: function (el, entry, target) {
if (el === this._activeEl) return;
this.active = true;
this.entry = entry;
this.$container.classList.add('active');
this.top = el.offsetTop - this.$container.offsetHeight - 10;
this.left = el.offsetLeft;
this.$container.setAttribute('style', 'left: ' + this.left + 'px; top: ' + this.top + 'px');
this.updatePermalink();
this.updateReferences();
this._activeEl = el;
if (this.top < document.body.scrollTop && el === target) {
// don't scroll unless it's a small thing (< 200px)
this.$container.scrollIntoView();
}
},
updatePermalink: function () {
this.$permalink.setAttribute('href', '#' + this.entry.id);
},
updateReferences: function () {
this.$refsLink.textContent = 'References (' + this.entry.referencingIds.length + ')';
},
activateIfMouseOver: function (e) {
var ref = this.findReferenceUnder(e.target);
if (ref && (!this.active || e.pageY > this._activeEl.offsetTop)) {
var entry = menu.search.biblio.byId[ref.id];
this.activate(ref.element, entry, e.target);
} else if (this.active && ((e.pageY < this.top) || e.pageY > (this._activeEl.offsetTop + this._activeEl.offsetHeight))) {
this.deactivate();
}
},
findReferenceUnder: function (el) {
while (el) {
var parent = el.parentNode;
if (el.nodeName === 'H1' && parent.nodeName.match(/EMU-CLAUSE|EMU-ANNEX|EMU-INTRO/) && parent.id) {
return { element: el, id: parent.id };
} else if (el.nodeName.match(/EMU-(?!CLAUSE|XREF|ANNEX|INTRO)|DFN/) &&
el.id && el.id[0] !== '_') {
if (el.nodeName === 'EMU-FIGURE' || el.nodeName === 'EMU-TABLE' || el.nodeName === 'EMU-EXAMPLE') {
// return the figcaption element
return { element: el.children[0].children[0], id: el.id };
} else if (el.nodeName === 'EMU-PRODUCTION') {
// return the LHS non-terminal element
return { element: el.children[0], id: el.id };
} else {
return { element: el, id: el.id };
}
}
el = parent;
}
},
deactivate: function () {
this.$container.classList.remove('active');
this._activeEl = null;
this.activeElBounds = null;
this.active = false;
}
}
var referencePane = {
init: function() {
this.$container = document.createElement('div');
this.$container.setAttribute('id', 'references-pane-container');
var $spacer = document.createElement('div');
$spacer.setAttribute('id', 'references-pane-spacer');
this.$pane = document.createElement('div');
this.$pane.setAttribute('id', 'references-pane');
this.$container.appendChild($spacer);
this.$container.appendChild(this.$pane);
this.$header = document.createElement('div');
this.$header.classList.add('menu-pane-header');
this.$header.textContent = 'References to ';
this.$headerRefId = document.createElement('a');
this.$header.appendChild(this.$headerRefId);
this.$closeButton = document.createElement('span');
this.$closeButton.setAttribute('id', 'references-pane-close');
this.$closeButton.addEventListener('click', function (e) {
this.deactivate();
}.bind(this));
this.$header.appendChild(this.$closeButton);
this.$pane.appendChild(this.$header);
var tableContainer = document.createElement('div');
tableContainer.setAttribute('id', 'references-pane-table-container');
this.$table = document.createElement('table');
this.$table.setAttribute('id', 'references-pane-table');
this.$tableBody = this.$table.createTBody();
tableContainer.appendChild(this.$table);
this.$pane.appendChild(tableContainer);
menu.$specContainer.appendChild(this.$container);
},
activate: function () {
this.$container.classList.add('active');
},
deactivate: function () {
this.$container.classList.remove('active');
},
showReferencesFor(entry) {
this.activate();
var newBody = document.createElement('tbody');
var previousId;
var previousCell;
var dupCount = 0;
this.$headerRefId.textContent = '#' + entry.id;
this.$headerRefId.setAttribute('href', '#' + entry.id);
entry.referencingIds.map(function (id) {
var target = document.getElementById(id);
var cid = findParentClauseId(target);
var clause = menu.search.biblio.byId[cid];
var dupCount = 0;
return { id: id, clause: clause }
}).sort(function (a, b) {
return sortByClauseNumber(a.clause, b.clause);
}).forEach(function (record, i) {
if (previousId === record.clause.id) {
previousCell.innerHTML += ' (<a href="#' + record.id + '">' + (dupCount + 2) + '</a>)';
dupCount++;
} else {
var row = newBody.insertRow();
var cell = row.insertCell();
cell.innerHTML = record.clause.number;
cell = row.insertCell();
cell.innerHTML = '<a href="#' + record.id + '">' + record.clause.titleHTML + '</a>';
previousCell = cell;
previousId = record.clause.id;
dupCount = 0;
}
}, this);
this.$table.removeChild(this.$tableBody);
this.$tableBody = newBody;
this.$table.appendChild(this.$tableBody);
}
}
function findParentClauseId(node) {
while (node && node.nodeName !== 'EMU-CLAUSE' && node.nodeName !== 'EMU-INTRO' && node.nodeName !== 'EMU-ANNEX') {
node = node.parentNode;
}
if (!node) return null;
return node.getAttribute('id');
}
function sortByClauseNumber(c1, c2) {
var c1c = c1.number.split('.');
var c2c = c2.number.split('.');
for (var i = 0; i < c1c.length; i++) {
if (i >= c2c.length) {
return 1;
}
var c1 = c1c[i];
var c2 = c2c[i];
var c1cn = Number(c1);
var c2cn = Number(c2);
if (Number.isNaN(c1cn) && Number.isNaN(c2cn)) {
if (c1 > c2) {
return 1;
} else if (c1 < c2) {
return -1;
}
} else if (!Number.isNaN(c1cn) && Number.isNaN(c2cn)) {
return -1;
} else if (Number.isNaN(c1cn) && !Number.isNaN(c2cn)) {
return 1;
} else if(c1cn > c2cn) {
return 1;
} else if (c1cn < c2cn) {
return -1;
}
}
if (c1c.length === c2c.length) {
return 0;
}
return -1;
}
document.addEventListener('DOMContentLoaded', function () {
Toolbox.init();
referencePane.init();
})
var CLAUSE_NODES = ['EMU-CLAUSE', 'EMU-INTRO', 'EMU-ANNEX'];
function findLocalReferences ($elem) {
var name = $elem.innerHTML;
var references = [];
var parentClause = $elem.parentNode;
while (parentClause && CLAUSE_NODES.indexOf(parentClause.nodeName) === -1) {
parentClause = parentClause.parentNode;
}
if(!parentClause) return;
var vars = parentClause.querySelectorAll('var');
for (var i = 0; i < vars.length; i++) {
var $var = vars[i];
if ($var.innerHTML === name) {
references.push($var);
}
}
return references;
}
function toggleFindLocalReferences($elem) {
var references = findLocalReferences($elem);
if ($elem.classList.contains('referenced')) {
references.forEach(function ($reference) {
$reference.classList.remove('referenced');
});
} else {
references.forEach(function ($reference) {
$reference.classList.add('referenced');
});
}
}
function installFindLocalReferences () {
document.addEventListener('click', function (e) {
if (e.target.nodeName === 'VAR') {
toggleFindLocalReferences(e.target);
}
});
}
document.addEventListener('DOMContentLoaded', installFindLocalReferences);
</script><style>body {
display: flex;
font-size: 18px;
line-height: 1.5;
font-family: Cambria, Palatino Linotype, Palatino, Liberation Serif, serif;
padding: 0;
margin: 0;
color: #111;
}
#spec-container {
padding: 0 20px;
flex-grow: 1;
flex-basis: 66%;
box-sizing: border-box;
overflow: hidden;
}
body.oldtoc {
margin: 0 auto;
}
a {
text-decoration: none;
color: #206ca7;
}
a:visited {
color: #206ca7;
}
a:hover {
text-decoration: underline;
color: #239dee;
}
code {
font-weight: bold;
font-family: Consolas, Monaco, monospace;
white-space: pre;
}
pre code {
font-weight: inherit;
}
pre code.hljs {
background-color: #fff;
margin: 0;
padding: 0;
}
ol.toc {
list-style: none;
padding-left: 0;
}
ol.toc ol.toc {
padding-left: 2ex;
list-style: none;
}
var {
color: #2aa198;
transition: background-color 0.25s ease;
cursor: pointer;
}
var.referenced {
background-color: #ffff33;
}
emu-const {
font-family: sans-serif;
}
emu-val {
font-weight: bold;
}
emu-alg ol, emu-alg ol ol ol ol {
list-style-type: decimal;
}
emu-alg ol ol, emu-alg ol ol ol ol ol {
list-style-type: lower-alpha;
}
emu-alg ol ol ol, ol ol ol ol ol ol {
list-style-type: lower-roman;
}
emu-eqn {
display: block;
margin-left: 4em;
}
emu-eqn.inline {
display: inline;
margin: 0;
}
emu-eqn div:first-child {
margin-left: -2em;
}
emu-note {
margin: 1em 0;
color: #666;
border-left: 5px solid #ccc;
display: flex;
flex-direction: row;
}
emu-note > span.note {
flex-basis: 100px;
min-width: 100px;
flex-grow: 0;
flex-shrink: 1;
text-transform: uppercase;
padding-left: 5px;
}
emu-note[type=editor] {
border-left-color: #faa;
}
emu-note > div.note-contents {
flex-grow: 1;
flex-shrink: 1;
}
emu-note > div.note-contents > p:first-of-type {
margin-top: 0;
}
emu-note > div.note-contents > p:last-of-type {
margin-bottom: 0;
}
emu-figure {
display: block;
}
emu-example {
display: block;
margin: 1em 3em;
}
emu-example figure figcaption {
margin-top: 0.5em;
text-align: left;
}
emu-figure figure,
emu-example figure,
emu-table figure {
display: flex;
flex-direction: column;
align-items: center;
}
emu-production {
display: block;
margin-top: 1em;
margin-bottom: 1em;
margin-left: 5ex;
}
emu-grammar.inline, emu-production.inline,
emu-grammar.inline emu-production emu-rhs, emu-production.inline emu-rhs,
emu-grammar[collapsed] emu-production emu-rhs, emu-production[collapsed] emu-rhs {
display: inline;
padding-left: 1ex;
margin-left: 0;
}
emu-grammar[collapsed] emu-production, emu-production[collapsed] {
margin: 0;
}
emu-constraints {
font-size: .75em;
margin-right: 1ex;
}
emu-gann {
margin-right: 1ex;
}
emu-gann emu-t:last-child,
emu-gann emu-nt:last-child {
margin-right: 0;
}
emu-geq {
margin-left: 1ex;
font-weight: bold;
}
emu-oneof {
font-weight: bold;
margin-left: 1ex;
}
emu-nt {
display: inline-block;
font-style: italic;
white-space: nowrap;
text-indent: 0;
}
emu-nt a, emu-nt a:visited {
color: #333;
}
emu-rhs emu-nt {
margin-right: 1ex;
}
emu-t {
display: inline-block;
font-family: monospace;
font-weight: bold;
white-space: nowrap;
text-indent: 0;
}
emu-production emu-t {
margin-right: 1ex;
}
emu-rhs {
display: block;
padding-left: 75px;
text-indent: -25px;
}
emu-mods {
font-size: .85em;
vertical-align: sub;
font-style: normal;
font-weight: normal;
}
emu-production[collapsed] emu-mods {
display: none;
}
emu-params, emu-opt {
margin-right: 1ex;
font-family: monospace;
}
emu-params, emu-constraints {
color: #2aa198;
}
emu-opt {
color: #b58900;
}
emu-gprose {
font-size: 0.9em;
font-family: Helvetica, Arial, sans-serif;
}
h1.shortname {
color: #f60;
font-size: 1.5em;
margin: 0;
}
h1.version {
color: #f60;
font-size: 1.5em;
margin: 0;
}
h1.title {
margin-top: 0;
color: #f60;
}
h1.first {
margin-top: 0;
}
h1, h2, h3, h4, h5, h6 {
position: relative;
}
h1 .secnum {
text-decoration: none;
margin-right: 10px;
}
h1 span.title {
order: 2;
}
h1 { font-size: 2.67em; margin-top: 2em; margin-bottom: 0; line-height: 1em;}
h2 { font-size: 2em; }
h3 { font-size: 1.56em; }
h4 { font-size: 1.25em; }
h5 { font-size: 1.11em; }
h6 { font-size: 1em; }
h1:hover span.utils {
display: block;
}
span.utils {
font-size: 18px;
line-height: 18px;
display: none;
position: absolute;
top: 100%;
left: 0;
right: 0;
font-weight: normal;
}
span.utils:before {
content: "⤷";
display: inline-block;
padding: 0 5px;
}
span.utils > * {
display: inline-block;
margin-right: 20px;
}
h1 span.utils span.anchor a,
h2 span.utils span.anchor a,
h3 span.utils span.anchor a,
h4 span.utils span.anchor a,
h5 span.utils span.anchor a,
h6 span.utils span.anchor a {
text-decoration: none;
font-variant: small-caps;
}
h1 span.utils span.anchor a:hover,
h2 span.utils span.anchor a:hover,
h3 span.utils span.anchor a:hover,
h4 span.utils span.anchor a:hover,
h5 span.utils span.anchor a:hover,
h6 span.utils span.anchor a:hover {
color: #333;
}
emu-intro h1, emu-clause h1, emu-annex h1 { font-size: 2em; }
emu-intro h2, emu-clause h2, emu-annex h2 { font-size: 1.56em; }
emu-intro h3, emu-clause h3, emu-annex h3 { font-size: 1.25em; }
emu-intro h4, emu-clause h4, emu-annex h4 { font-size: 1.11em; }
emu-intro h5, emu-clause h5, emu-annex h5 { font-size: 1em; }
emu-intro h6, emu-clause h6, emu-annex h6 { font-size: 0.9em; }
emu-intro emu-intro h1, emu-clause emu-clause h1, emu-annex emu-annex h1 { font-size: 1.56em; }
emu-intro emu-intro h2, emu-clause emu-clause h2, emu-annex emu-annex h2 { font-size: 1.25em; }
emu-intro emu-intro h3, emu-clause emu-clause h3, emu-annex emu-annex h3 { font-size: 1.11em; }
emu-intro emu-intro h4, emu-clause emu-clause h4, emu-annex emu-annex h4 { font-size: 1em; }
emu-intro emu-intro h5, emu-clause emu-clause h5, emu-annex emu-annex h5 { font-size: 0.9em; }
emu-intro emu-intro emu-intro h1, emu-clause emu-clause emu-clause h1, emu-annex emu-annex emu-annex h1 { font-size: 1.25em; }
emu-intro emu-intro emu-intro h2, emu-clause emu-clause emu-clause h2, emu-annex emu-annex emu-annex h2 { font-size: 1.11em; }
emu-intro emu-intro emu-intro h3, emu-clause emu-clause emu-clause h3, emu-annex emu-annex emu-annex h3 { font-size: 1em; }
emu-intro emu-intro emu-intro h4, emu-clause emu-clause emu-clause h4, emu-annex emu-annex emu-annex h4 { font-size: 0.9em; }
emu-intro emu-intro emu-intro emu-intro h1, emu-clause emu-clause emu-clause emu-clause h1, emu-annex emu-annex emu-annex emu-annex h1 { font-size: 1.11em; }
emu-intro emu-intro emu-intro emu-intro h2, emu-clause emu-clause emu-clause emu-clause h2, emu-annex emu-annex emu-annex emu-annex h2 { font-size: 1em; }
emu-intro emu-intro emu-intro emu-intro h3, emu-clause emu-clause emu-clause emu-clause h3, emu-annex emu-annex emu-annex emu-annex h3 { font-size: 0.9em; }
emu-intro emu-intro emu-intro emu-intro emu-intro h1, emu-clause emu-clause emu-clause emu-clause emu-clause h1, emu-annex emu-annex emu-annex emu-annex emu-annex h1 { font-size: 1em; }
emu-intro emu-intro emu-intro emu-intro emu-intro h2, emu-clause emu-clause emu-clause emu-clause emu-clause h2, emu-annex emu-annex emu-annex emu-annex emu-annex h2 { font-size: 0.9em; }
emu-intro emu-intro emu-intro emu-intro emu-intro emu-intro h1, emu-clause emu-clause emu-clause emu-clause emu-clause emu-clause h1, emu-annex emu-annex emu-annex emu-annex emu-annex emu-annex h1 { font-size: 0.9em }
emu-clause, emu-intro, emu-annex {
display: block;
}
/* Figures and tables */
figure { display: block; margin: 1em 0 3em 0; }
figure object { display: block; margin: 0 auto; }
figure table.real-table { margin: 0 auto; }
figure figcaption {
display: block;
color: #555555;
font-weight: bold;
text-align: center;
}
emu-table table {
margin: 0 auto;
}
emu-table table, table.real-table {
border-collapse: collapse;
}
emu-table td, emu-table th, table.real-table td, table.real-table th {
border: 1px solid black;
padding: 0.4em;
vertical-align: baseline;
}
emu-table th, emu-table thead td, table.real-table th {
background-color: #eeeeee;
}
/* Note: the left content edges of table.lightweight-table >tbody >tr >td
and div.display line up. */
table.lightweight-table {
border-collapse: collapse;
margin: 0 0 0 1.5em;
}
table.lightweight-table td, table.lightweight-table th {
border: none;
padding: 0 0.5em;
vertical-align: baseline;
}
/* diff styles */
ins {
background-color: #e0f8e0;
text-decoration: none;
border-bottom: 1px solid #396;
}
del {
background-color: #fee;
}
ins.block, del.block,
emu-production > ins, emu-production > del,
emu-grammar > ins, emu-grammar > del {
display: block;
}
emu-rhs > ins, emu-rhs > del {
display: inline;
}
tr.ins > td > ins {
border-bottom: none;
}
tr.ins > td {
background-color: #e0f8e0;
}
tr.del > td {
background-color: #fee;
}
/* Menu Styles */
#menu-toggle {
font-size: 2em;
position: fixed;
top: 0;
left: 0;
width: 1.5em;
height: 1.5em;
z-index: 3;
visibility: hidden;
color: #1567a2;
background-color: #fff;
line-height: 1.5em;
text-align: center;
-webkit-touch-callout: none;
-webkit-user-select: none;
-khtml-user-select: none;
-moz-user-select: none;
-ms-user-select: none;
user-select: none;;
cursor: pointer;
}
#menu {
display: flex;
flex-direction: column;
width: 33%; height: 100vh;
max-width: 500px;
box-sizing: border-box;
background-color: #ddd;
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</style></head><body><div id="menu-toggle">☰</div><div id="menu-spacer"></div><div id="menu"><div id="menu-search"><input type="text" id="menu-search-box" placeholder="Search..."><div id="menu-search-results" class="inactive"></div></div><div id="menu-pins"><div class="menu-pane-header">Pins</div><ul id="menu-pins-list"></ul></div><div class="menu-pane-header">Table of Contents</div><div id="menu-toc"><ol class="toc"><li><span class="item-toggle-none"></span><a href="#introduction" title="Metadata Proposal - ECMAScript">Metadata Proposal - ECMAScript</a></li><li><span class="item-toggle-none"></span><a href="#syntax" title="Syntax"><span class="secnum">1</span> Syntax</a></li><li><span class="item-toggle">◢</span><a href="#abstract-operations" title="Abstract Operations"><span class="secnum">2</span> Abstract Operations</a><ol class="toc"><li><span class="item-toggle">◢</span><a href="#operations-on-objects" title="Operations on Objects"><span class="secnum">2.1</span> Operations on Objects</a><ol class="toc"><li><span class="item-toggle-none"></span><a href="#getorcreatemetadatamap" title="GetOrCreateMetadataMap ( O, P, Create )"><span class="secnum">2.1.1</span> GetOrCreateMetadataMap ( O, P, Create )</a></li></ol></li></ol></li><li><span class="item-toggle">◢</span><a href="#ordinary-and-exotic-objects-behaviors" title="Ordinary and Exotic Objects Behaviors"><span class="secnum">3</span> Ordinary and Exotic Objects Behaviors</a><ol class="toc"><li><span class="item-toggle">◢</span><a href="#ordinary-object-internal-methods-and-internal-slots" title="Ordinary Object Internal Methods and Internal Slots"><span class="secnum">3.1</span> Ordinary Object Internal Methods and Internal Slots</a><ol class="toc"><li><span class="item-toggle">◢</span><a href="#ordinary-object-internal-methods-and-internal-slots-hasmetadata" title="[[HasMetadata]] ( MetadataKey, P )"><span class="secnum">3.1.1</span> [[HasMetadata]] ( MetadataKey, P )</a><ol class="toc"><li><span class="item-toggle-none"></span><a href="#ordinaryhasmetadata" title="OrdinaryHasMetadata ( MetadataKey, O, P )"><span class="secnum">3.1.1.1</span> OrdinaryHasMetadata ( MetadataKey, O, P )</a></li></ol></li><li><span class="item-toggle">◢</span><a href="#ordinary-object-internal-methods-and-internal-slots-hasownmetadata" title="[[HasOwnMetadata]] ( MetadataKey, P )"><span class="secnum">3.1.2</span> [[HasOwnMetadata]] ( MetadataKey, P )</a><ol class="toc"><li><span class="item-toggle-none"></span><a href="#ordinaryhasownmetadata" title="OrdinaryHasOwnMetadata ( MetadataKey, O, P )"><span class="secnum">3.1.2.1</span> OrdinaryHasOwnMetadata ( MetadataKey, O, P )</a></li></ol></li><li><span class="item-toggle">◢</span><a href="#ordinary-object-internal-methods-and-internal-slots-getmetadata" title="[[GetMetadata]] ( MetadataKey, P )"><span class="secnum">3.1.3</span> [[GetMetadata]] ( MetadataKey, P )</a><ol class="toc"><li><span class="item-toggle-none"></span><a href="#ordinarygetmetadata" title="OrdinaryGetMetadata ( MetadataKey, O, P )"><span class="secnum">3.1.3.1</span> OrdinaryGetMetadata ( MetadataKey, O, P )</a></li></ol></li><li><span class="item-toggle">◢</span><a href="#ordinary-object-internal-methods-and-internal-slots-getownmetadata" title="[[GetOwnMetadata]] ( MetadataKey, P, ParamIndex )"><span class="secnum">3.1.4</span> [[GetOwnMetadata]] ( MetadataKey, P, ParamIndex )</a><ol class="toc"><li><span class="item-toggle-none"></span><a href="#ordinarygetownmetadata" title="OrdinaryGetOwnMetadata ( MetadataKey, O, P )"><span class="secnum">3.1.4.1</span> OrdinaryGetOwnMetadata ( MetadataKey, O, P )</a></li></ol></li><li><span class="item-toggle">◢</span><a href="#ordinary-object-internal-methods-and-internal-slots-defineownmetadata" title="[[DefineOwnMetadata]] ( MetadataKey, MetadataValue, P )"><span class="secnum">3.1.5</span> [[DefineOwnMetadata]] ( MetadataKey, MetadataValue, P )</a><ol class="toc"><li><span class="item-toggle-none"></span><a href="#ordinarydefineownmetadata" title="OrdinaryDefineOwnMetadata ( MetadataKey, MetadataValue, O, P )"><span class="secnum">3.1.5.1</span> OrdinaryDefineOwnMetadata ( MetadataKey, MetadataValue, O, P )</a></li></ol></li><li><span class="item-toggle">◢</span><a href="#ordinary-object-internal-methods-and-internal-slots-metadatakeys" title="[[MetadataKeys]] ( P )"><span class="secnum">3.1.6</span> [[MetadataKeys]] ( P )</a><ol class="toc"><li><span class="item-toggle-none"></span><a href="#ordinarymetadatakeys" title="OrdinaryMetadataKeys ( O, P )"><span class="secnum">3.1.6.1</span> OrdinaryMetadataKeys ( O, P )</a></li></ol></li><li><span class="item-toggle">◢</span><a href="#ordinary-object-internal-methods-and-internal-slots-ownmetadatakeys" title="[[OwnMetadataKeys]] ( P )"><span class="secnum">3.1.7</span> [[OwnMetadataKeys]] ( P )</a><ol class="toc"><li><span class="item-toggle-none"></span><a href="#ordinaryownmetadatakeys" title="OrdinaryOwnMetadataKeys ( O, P )"><span class="secnum">3.1.7.1</span> OrdinaryOwnMetadataKeys ( O, P )</a></li></ol></li><li><span class="item-toggle-none"></span><a href="#ordinary-object-internal-methods-and-internal-slots-deletemetadata" title="[[DeleteMetadata]]( MetadataKey, P )"><span class="secnum">3.1.8</span> [[DeleteMetadata]]( MetadataKey, P )</a></li></ol></li></ol></li><li><span class="item-toggle">◢</span><a href="#reflection" title="Reflection"><span class="secnum">4</span> Reflection</a><ol class="toc"><li><span class="item-toggle">◢</span><a href="#reflect" title="The Reflect Object"><span class="secnum">4.1</span> The Reflect Object</a><ol class="toc"><li><span class="item-toggle-none"></span><a href="#reflect-metadatadecoratorfunctions" title="Metadata Decorator Functions"><span class="secnum">4.1.1</span> Metadata Decorator Functions</a></li><li><span class="item-toggle-none"></span><a href="#reflect.metadata" title="Reflect.metadata ( metadataKey, metadataValue )"><span class="secnum">4.1.2</span> Reflect.metadata ( metadataKey, metadataValue )</a></li><li><span class="item-toggle-none"></span><a href="#reflect.definemetadata" title="Reflect.defineMetadata ( metadataKey, metadataValue, target [, propertyKey] )"><span class="secnum">4.1.3</span> Reflect.defineMetadata ( metadataKey, metadataValue, target [, propertyKey] )</a></li><li><span class="item-toggle-none"></span><a href="#reflect.hasmetadata" title="Reflect.hasMetadata ( metadataKey, target [, propertyKey] )"><span class="secnum">4.1.4</span> Reflect.hasMetadata ( metadataKey, target [, propertyKey] )</a></li><li><span class="item-toggle-none"></span><a href="#reflect.hasownmetadata" title="Reflect.hasOwnMetadata ( metadataKey, target [, propertyKey] )"><span class="secnum">4.1.5</span> Reflect.hasOwnMetadata ( metadataKey, target [, propertyKey] )</a></li><li><span class="item-toggle-none"></span><a href="#reflect.getmetadata" title="Reflect.getMetadata ( metadataKey, target [, propertyKey] )"><span class="secnum">4.1.6</span> Reflect.getMetadata ( metadataKey, target [, propertyKey] )</a></li><li><span class="item-toggle-none"></span><a href="#reflect.getownmetadata" title="Reflect.getOwnMetadata ( metadataKey, target [, propertyKey] )"><span class="secnum">4.1.7</span> Reflect.getOwnMetadata ( metadataKey, target [, propertyKey] )</a></li><li><span class="item-toggle-none"></span><a href="#reflect.getmetadatakeys" title="Reflect.getMetadataKeys ( target [, propertyKey] )"><span class="secnum">4.1.8</span> Reflect.getMetadataKeys ( target [, propertyKey] )</a></li><li><span class="item-toggle-none"></span><a href="#reflect.getownmetadatakeys" title="Reflect.getOwnMetadataKeys ( target [, propertyKey] )"><span class="secnum">4.1.9</span> Reflect.getOwnMetadataKeys ( target [, propertyKey] )</a></li><li><span class="item-toggle-none"></span><a href="#reflect.deletemetadata" title="Reflect.deleteMetadata ( metadataKey, target [, propertyKey] )"><span class="secnum">4.1.10</span> Reflect.deleteMetadata ( metadataKey, target [, propertyKey] )</a></li></ol></li></ol></li></ol></div></div><div id="spec-container">
<emu-intro id="introduction">
<h1 class="first">Metadata Proposal - ECMAScript</h1>
<emu-note><span class="note">Note</span><div class="note-contents">A shim for this API can be found here: <a href="https://github.com/rbuckton/ReflectDecorators">https://github.com/rbuckton/ReflectDecorators</a></div></emu-note>
<p>Proposal to add Metadata to ECMAScript.</p>
</emu-intro>
<emu-clause id="syntax">
<h1><span class="secnum">1</span>Syntax</h1>
<emu-note><span class="note">Note</span><div class="note-contents">This section is non-normative.</div></emu-note>
<pre><code class="javascript hljs"><span class="hljs-comment">// define metadata on an object or property</span>
<span class="hljs-built_in">Reflect</span>.defineMetadata(metadataKey, metadataValue, target);
<span class="hljs-built_in">Reflect</span>.defineMetadata(metadataKey, metadataValue, target, propertyKey);
<span class="hljs-comment">// check for presence of a metadata key on the prototype chain of an object or property</span>
<span class="hljs-keyword">let</span> result = <span class="hljs-built_in">Reflect</span>.hasMetadata(metadataKey, target);
<span class="hljs-keyword">let</span> result = <span class="hljs-built_in">Reflect</span>.hasMetadata(metadataKey, target, propertyKey);
<span class="hljs-comment">// check for presence of an own metadata key of an object or property</span>
<span class="hljs-keyword">let</span> result = <span class="hljs-built_in">Reflect</span>.hasOwnMetadata(metadataKey, target);
<span class="hljs-keyword">let</span> result = <span class="hljs-built_in">Reflect</span>.hasOwnMetadata(metadataKey, target, propertyKey);
<span class="hljs-comment">// get metadata value of a metadata key on the prototype chain of an object or property</span>
<span class="hljs-keyword">let</span> result = <span class="hljs-built_in">Reflect</span>.getMetadata(metadataKey, target);
<span class="hljs-keyword">let</span> result = <span class="hljs-built_in">Reflect</span>.getMetadata(metadataKey, target, propertyKey);
<span class="hljs-comment">// get metadata value of an own metadata key of an object or property</span>
<span class="hljs-keyword">let</span> result = <span class="hljs-built_in">Reflect</span>.getOwnMetadata(metadataKey, target);
<span class="hljs-keyword">let</span> result = <span class="hljs-built_in">Reflect</span>.getOwnMetadata(metadataKey, target, propertyKey);
<span class="hljs-comment">// get all metadata keys on the prototype chain of an object or property</span>
<span class="hljs-keyword">let</span> result = <span class="hljs-built_in">Reflect</span>.getMetadataKeys(target);
<span class="hljs-keyword">let</span> result = <span class="hljs-built_in">Reflect</span>.getMetadataKeys(target, propertyKey);
<span class="hljs-comment">// get all own metadata keys of an object or property</span>
<span class="hljs-keyword">let</span> result = <span class="hljs-built_in">Reflect</span>.getOwnMetadataKeys(target);
<span class="hljs-keyword">let</span> result = <span class="hljs-built_in">Reflect</span>.getOwnMetadataKeys(target, propertyKey);
<span class="hljs-comment">// delete metadata from an object or property</span>
<span class="hljs-keyword">let</span> result = <span class="hljs-built_in">Reflect</span>.deleteMetadata(metadataKey, target);
<span class="hljs-keyword">let</span> result = <span class="hljs-built_in">Reflect</span>.deleteMetadata(metadataKey, target, propertyKey);
<span class="hljs-comment">// apply metadata via a decorator to a constructor</span>
@<span class="hljs-built_in">Reflect</span>.metadata(metadataKey, metadataValue)
<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">C</span> </span>{
<span class="hljs-comment">// apply metadata via a decorator to a method (property)</span>
@<span class="hljs-built_in">Reflect</span>.metadata(metadataKey, metadataValue)
method() {
}
}
<span class="hljs-comment">// Design-time type annotations</span>
<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">Type</span>(<span class="hljs-params">type</span>) </span>{ <span class="hljs-keyword">return</span> <span class="hljs-built_in">Reflect</span>.metadata(<span class="hljs-string">"design:type"</span>, type); }
<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">ParamTypes</span>(<span class="hljs-params">...types</span>) </span>{ <span class="hljs-keyword">return</span> <span class="hljs-built_in">Reflect</span>.metadata(<span class="hljs-string">"design:paramtypes"</span>, types); }
<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">ReturnType</span>(<span class="hljs-params">type</span>) </span>{ <span class="hljs-keyword">return</span> <span class="hljs-built_in">Reflect</span>.metadata(<span class="hljs-string">"design:returntype"</span>, type); }
<span class="hljs-comment">// Decorator application</span>
@ParamTypes(<span class="hljs-built_in">String</span>, <span class="hljs-built_in">Number</span>)
<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">C</span> </span>{
<span class="hljs-keyword">constructor</span>(text, i) {
}
@Type(<span class="hljs-built_in">String</span>)
get name() { <span class="hljs-keyword">return</span> <span class="hljs-string">"text"</span>; }
@Type(<span class="hljs-built_in">Function</span>)
@ParamTypes(<span class="hljs-built_in">Number</span>, <span class="hljs-built_in">Number</span>)
@ReturnType(<span class="hljs-built_in">Number</span>)
add(x, y) {
<span class="hljs-keyword">return</span> x + y;
}
}
<span class="hljs-comment">// Metadata introspection</span>
<span class="hljs-keyword">let</span> obj = <span class="hljs-keyword">new</span> C(<span class="hljs-string">"a"</span>, <span class="hljs-number">1</span>);
<span class="hljs-keyword">let</span> paramTypes = <span class="hljs-built_in">Reflect</span>.getMetadata(<span class="hljs-string">"design:paramtypes"</span>, inst, <span class="hljs-string">"add"</span>); <span class="hljs-comment">// [Number, Number]</span></code></pre>
</emu-clause>
<emu-clause id="abstract-operations">
<h1><span class="secnum">2</span>Abstract Operations</h1>
<emu-clause id="operations-on-objects">
<h1><span class="secnum">2.1</span>Operations on Objects</h1>
<emu-clause id="getorcreatemetadatamap" aoid="GetOrCreateMetadataMap">
<h1><span class="secnum">2.1.1</span>GetOrCreateMetadataMap ( O, P, Create )</h1>
<p>When the abstract operation GetOrCreateMetadataMap is called with Object <var>O</var>, property key <var>P</var>, and Boolean <var>Create</var> the following steps are taken:</p>
<emu-alg><ol><li>Assert: <var>P</var> is <emu-val>undefined</emu-val> or <emu-xref aoid="IsPropertyKey" id="_ref_0"><a href="https://tc39.github.io/ecma262/#sec-ispropertykey">IsPropertyKey</a></emu-xref>(<var>P</var>) is <emu-val>true</emu-val>.</li><li>Let <var>targetMetadata</var> be the value of <var>O</var>'s [[Metadata]] internal slot.</li><li>If <var>targetMetadata</var> is <emu-val>undefined</emu-val>, then<ol><li>If <var>Create</var> is <emu-val>false</emu-val>, return <emu-val>undefined</emu-val>.</li><li>Set <var>targetMetadata</var> to be a newly created <emu-val>Map</emu-val> object.</li><li>Set the [[Metadata]] internal slot of <var>O</var> to <var>targetMetadata</var>.</li></ol></li><li>Let <var>metadataMap</var> be ? <emu-xref aoid="Invoke" id="_ref_1"><a href="https://tc39.github.io/ecma262/#sec-invoke">Invoke</a></emu-xref>(<var>targetMetadata</var>, <code>"get"</code>, <var>P</var>).</li><li>If <var>metadataMap</var> is <emu-val>undefined</emu-val>, then<ol><li>If <var>Create</var> is <emu-val>false</emu-val>, return <emu-val>undefined</emu-val>.</li><li>Set <var>metadataMap</var> to be a newly created <emu-val>Map</emu-val> object.</li><li>Perform ? <emu-xref aoid="Invoke" id="_ref_2"><a href="https://tc39.github.io/ecma262/#sec-invoke">Invoke</a></emu-xref>(<var>targetMetadata</var>, <code>"set"</code>, <var>P</var>, <var>metadataMap</var>).</li></ol></li><li>Return <var>metadataMap</var>.
</li></ol></emu-alg>
</emu-clause>
</emu-clause>
</emu-clause>
<emu-clause id="ordinary-and-exotic-objects-behaviors">
<h1><span class="secnum">3</span>Ordinary and Exotic Objects Behaviors</h1>
<emu-clause id="ordinary-object-internal-methods-and-internal-slots">
<h1><span class="secnum">3.1</span>Ordinary Object Internal Methods and Internal Slots</h1>
<p>All ordinary objects have an internal slot called [[Metadata]]. The value of this internal slot is either <emu-val>null</emu-val> or a <emu-val>Map</emu-val> object and is used for storing metadata for an object.</p>
<emu-clause id="ordinary-object-internal-methods-and-internal-slots-hasmetadata">
<h1><span class="secnum">3.1.1</span>[[HasMetadata]] ( MetadataKey, P )</h1>
<p>When the [[HasMetadata]] internal method of <var>O</var> is called with <emu-xref href="#sec-ecmascript-language-types"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">ECMAScript language value</a></emu-xref> <var>MetadataKey</var> and property key <var>P</var>, the following steps are taken:</p>
<emu-alg><ol><li>Return ? <emu-xref aoid="OrdinaryHasMetadata" id="_ref_3"><a href="#ordinaryhasmetadata">OrdinaryHasMetadata</a></emu-xref>(<var>MetadataKey</var>, <var>O</var>, <var>P</var>).
</li></ol></emu-alg>
<emu-clause id="ordinaryhasmetadata" aoid="OrdinaryHasMetadata">
<h1><span class="secnum">3.1.1.1</span>OrdinaryHasMetadata ( MetadataKey, O, P )</h1>
<p>When the abstract operation OrdinaryHasMetadata is called with <emu-xref href="#sec-ecmascript-language-types"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">ECMAScript language value</a></emu-xref> <var>MetadataKey</var>, Object <var>O</var>, and property key <var>P</var>, the following steps are taken:</p>
<emu-alg><ol><li>Assert: <var>P</var> is <emu-val>undefined</emu-val> or <emu-xref aoid="IsPropertyKey" id="_ref_4"><a href="https://tc39.github.io/ecma262/#sec-ispropertykey">IsPropertyKey</a></emu-xref>(<var>P</var>) is <emu-val>true</emu-val>.</li><li>Let <var>hasOwn</var> be ? <emu-xref aoid="OrdinaryHasOwnMetadata" id="_ref_5"><a href="#ordinaryhasownmetadata">OrdinaryHasOwnMetadata</a></emu-xref>(<var>MetadataKey</var>, <var>O</var>, <var>P</var>).</li><li>If <var>hasOwn</var> is <emu-val>true</emu-val>, return <emu-val>true</emu-val>.</li><li>Let <var>parent</var> be ? <var>O</var>.[[GetPrototypeOf]]().</li><li>If <var>parent</var> is not <emu-val>null</emu-val>, Return ? <var>parent</var>.[[HasMetadata]](<var>MetadataKey</var>, <var>P</var>).</li><li>Return <emu-val>false</emu-val>.
</li></ol></emu-alg>
</emu-clause>
</emu-clause>
<emu-clause id="ordinary-object-internal-methods-and-internal-slots-hasownmetadata">
<h1><span class="secnum">3.1.2</span>[[HasOwnMetadata]] ( MetadataKey, P )</h1>
<p>When the [[HasOwnMetadata]] internal method of <var>O</var> is called with <emu-xref href="#sec-ecmascript-language-types"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">ECMAScript language value</a></emu-xref> <var>MetadataKey</var> and property key <var>P</var>, the following steps are taken:</p>
<emu-alg><ol><li>Return ? <emu-xref aoid="OrdinaryHasOwnMetadata" id="_ref_6"><a href="#ordinaryhasownmetadata">OrdinaryHasOwnMetadata</a></emu-xref>(<var>MetadataKey</var>, <var>O</var>, <var>P</var>).
</li></ol></emu-alg>
<emu-clause id="ordinaryhasownmetadata" aoid="OrdinaryHasOwnMetadata">
<h1><span class="secnum">3.1.2.1</span>OrdinaryHasOwnMetadata ( MetadataKey, O, P )</h1>
<p>When the abstract operation OrdinaryHasOwnMetadata is called with <emu-xref href="#sec-ecmascript-language-types"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">ECMAScript language value</a></emu-xref> <var>MetadataKey</var>, Object <var>O</var>, and property key <var>P</var>, the following steps are taken:</p>
<emu-alg><ol><li>Assert: <var>P</var> is <emu-val>undefined</emu-val> or <emu-xref aoid="IsPropertyKey" id="_ref_7"><a href="https://tc39.github.io/ecma262/#sec-ispropertykey">IsPropertyKey</a></emu-xref>(<var>P</var>) is <emu-val>true</emu-val>.</li><li>Let <var>metadataMap</var> be ? <emu-xref aoid="GetOrCreateMetadataMap" id="_ref_8"><a href="#getorcreatemetadatamap">GetOrCreateMetadataMap</a></emu-xref>(<var>O</var>, <var>P</var>, <emu-val>false</emu-val>).</li><li>If <var>metadataMap</var> is <emu-val>undefined</emu-val>, return <emu-val>false</emu-val>.</li><li>Return ? <emu-xref aoid="ToBoolean" id="_ref_9"><a href="https://tc39.github.io/ecma262/#sec-toboolean">ToBoolean</a></emu-xref>(? <emu-xref aoid="Invoke" id="_ref_10"><a href="https://tc39.github.io/ecma262/#sec-invoke">Invoke</a></emu-xref>(<var>metadataMap</var>, <code>"has"</code>, <var>MetadataKey</var>)).
</li></ol></emu-alg>
</emu-clause>
</emu-clause>
<emu-clause id="ordinary-object-internal-methods-and-internal-slots-getmetadata">
<h1><span class="secnum">3.1.3</span>[[GetMetadata]] ( MetadataKey, P )</h1>
<p>When the [[GetMatadata]] internal method of <var>O</var> is called with <emu-xref href="#sec-ecmascript-language-types"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">ECMAScript language value</a></emu-xref> <var>MetadataKey</var> and property key <var>P</var>, the following steps are taken:</p>
<emu-alg><ol><li>Return ? <emu-xref aoid="OrdinaryGetMetadata" id="_ref_11"><a href="#ordinarygetmetadata">OrdinaryGetMetadata</a></emu-xref>(<var>MetadataKey</var>, <var>O</var>, <var>P</var>).
</li></ol></emu-alg>
<emu-clause id="ordinarygetmetadata" aoid="OrdinaryGetMetadata">
<h1><span class="secnum">3.1.3.1</span>OrdinaryGetMetadata ( MetadataKey, O, P )</h1>
<p>When the abstract operation OrdinaryGetMetadata is called with <emu-xref href="#sec-ecmascript-language-types"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">ECMAScript language value</a></emu-xref> <var>MetadataKey</var>, Object <var>O</var>, and property key <var>P</var>, the following steps are taken:</p>
<emu-alg><ol><li>Assert: <var>P</var> is <emu-val>undefined</emu-val> or <emu-xref aoid="IsPropertyKey" id="_ref_12"><a href="https://tc39.github.io/ecma262/#sec-ispropertykey">IsPropertyKey</a></emu-xref>(<var>P</var>) is <emu-val>true</emu-val>.</li><li>Let <var>hasOwn</var> be ? <emu-xref aoid="OrdinaryHasOwnMetadata" id="_ref_13"><a href="#ordinaryhasownmetadata">OrdinaryHasOwnMetadata</a></emu-xref>(<var>MetadataKey</var>, <var>O</var>, <var>P</var>).</li><li>If <var>hasOwn</var> is <emu-val>true</emu-val>, return ? <emu-xref aoid="OrdinaryGetOwnMetadata" id="_ref_14"><a href="#ordinarygetownmetadata">OrdinaryGetOwnMetadata</a></emu-xref>(<var>MetadataKey</var>, <var>O</var>, <var>P</var>).</li><li>Let <var>parent</var> be ? <var>O</var>.[[GetPrototypeOf]]().</li><li>If <var>parent</var> is not <emu-val>null</emu-val>, return ? <var>parent</var>.[[GetMetadata]](<var>MetadataKey</var>, <var>P</var>).</li><li>Return <emu-val>undefined</emu-val>.
</li></ol></emu-alg>
</emu-clause>
</emu-clause>
<emu-clause id="ordinary-object-internal-methods-and-internal-slots-getownmetadata">
<h1><span class="secnum">3.1.4</span>[[GetOwnMetadata]] ( MetadataKey, P, ParamIndex )</h1>
<p>When the [[GetOwnMetadata]] internal method of <var>O</var> is called with <emu-xref href="#sec-ecmascript-language-types"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">ECMAScript language value</a></emu-xref> <var>MetadataKey</var> and property key <var>P</var>, the following steps are taken:</p>
<emu-alg><ol><li>Return ? <emu-xref aoid="OrdinaryGetOwnMetadata" id="_ref_15"><a href="#ordinarygetownmetadata">OrdinaryGetOwnMetadata</a></emu-xref>(<var>MetadataKey</var>, <var>O</var>, <var>P</var>).
</li></ol></emu-alg>
<emu-clause id="ordinarygetownmetadata" aoid="OrdinaryGetOwnMetadata">
<h1><span class="secnum">3.1.4.1</span>OrdinaryGetOwnMetadata ( MetadataKey, O, P )</h1>
<p>When the abstract operation OrdinaryGetOwnMetadata is called with <emu-xref href="#sec-ecmascript-language-types"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">ECMAScript language value</a></emu-xref> <var>MetadataKey</var>, Object <var>O</var>, and property key <var>P</var>, the following steps are taken:</p>
<emu-alg><ol><li>Assert: <var>P</var> is <emu-val>undefined</emu-val> or <emu-xref aoid="IsPropertyKey" id="_ref_16"><a href="https://tc39.github.io/ecma262/#sec-ispropertykey">IsPropertyKey</a></emu-xref>(<var>P</var>) is <emu-val>true</emu-val>.</li><li>Let <var>metadataMap</var> be ? <emu-xref aoid="GetOrCreateMetadataMap" id="_ref_17"><a href="#getorcreatemetadatamap">GetOrCreateMetadataMap</a></emu-xref>(<var>O</var>, <var>P</var>, <emu-val>false</emu-val>).</li><li>If <var>metadataMap</var> is <emu-val>undefined</emu-val>, return <emu-val>undefined</emu-val>.</li><li>Return ? <emu-xref aoid="Invoke" id="_ref_18"><a href="https://tc39.github.io/ecma262/#sec-invoke">Invoke</a></emu-xref>(<var>metadataMap</var>, <code>"get"</code>, <var>MetadataKey</var>).
</li></ol></emu-alg>
</emu-clause>
</emu-clause>
<emu-clause id="ordinary-object-internal-methods-and-internal-slots-defineownmetadata">
<h1><span class="secnum">3.1.5</span>[[DefineOwnMetadata]] ( MetadataKey, MetadataValue, P )</h1>
<p>When the [[DefineOwnMetadata]] internal method of <var>O</var> is called with <emu-xref href="#sec-ecmascript-language-types"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">ECMAScript language value</a></emu-xref> <var>MetadataKey</var>, <emu-xref href="#sec-ecmascript-language-types"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">ECMAScript language value</a></emu-xref> <var>MetadataValue</var>, and property key <var>P</var>, the following steps are taken:</p>
<emu-alg><ol><li>Return ? <emu-xref aoid="OrdinaryDefineOwnMetadata" id="_ref_19"><a href="#ordinarydefineownmetadata">OrdinaryDefineOwnMetadata</a></emu-xref>(<var>MetadataKey</var>, <var>MetadataValue</var>, <var>O</var>, <var>P</var>)
</li></ol></emu-alg>
<emu-clause id="ordinarydefineownmetadata" aoid="OrdinaryDefineOwnMetadata">
<h1><span class="secnum">3.1.5.1</span>OrdinaryDefineOwnMetadata ( MetadataKey, MetadataValue, O, P )</h1>
<p>When the abstract operation <emu-xref aoid="OrdinaryDefineOwnProperty" id="_ref_20"><a href="https://tc39.github.io/ecma262/#sec-ordinarydefineownproperty">OrdinaryDefineOwnProperty</a></emu-xref> is called with <emu-xref href="#sec-ecmascript-language-types"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">ECMAScript language value</a></emu-xref> <var>MetadataKey</var>, <emu-xref href="#sec-ecmascript-language-types"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">ECMAScript language value</a></emu-xref> <var>MetadataValue</var>, Object <var>O</var>, and property key <var>P</var>, the following steps are taken:</p>
<emu-alg><ol><li>Assert: <var>P</var> is <emu-val>undefined</emu-val> or <emu-xref aoid="IsPropertyKey" id="_ref_21"><a href="https://tc39.github.io/ecma262/#sec-ispropertykey">IsPropertyKey</a></emu-xref>(<var>P</var>) is <emu-val>true</emu-val>.</li><li>Let <var>metadataMap</var> be ? <emu-xref aoid="GetOrCreateMetadataMap" id="_ref_22"><a href="#getorcreatemetadatamap">GetOrCreateMetadataMap</a></emu-xref>(<var>O</var>, <var>P</var>, <emu-val>true</emu-val>).</li><li>Return ? <emu-xref aoid="Invoke" id="_ref_23"><a href="https://tc39.github.io/ecma262/#sec-invoke">Invoke</a></emu-xref>(<var>metadataMap</var>, <code>"set"</code>, <var>MetadataKey</var>, <var>MetadataValue</var>).
</li></ol></emu-alg>
</emu-clause>
</emu-clause>
<emu-clause id="ordinary-object-internal-methods-and-internal-slots-metadatakeys">
<h1><span class="secnum">3.1.6</span>[[MetadataKeys]] ( P )</h1>
<p>When the [[MetadataKeys]] internal method of <var>O</var> is called with property key <var>P</var> the following steps are taken:</p>
<emu-alg><ol><li>Return ? <emu-xref aoid="OrdinaryMetadataKeys" id="_ref_24"><a href="#ordinarymetadatakeys">OrdinaryMetadataKeys</a></emu-xref>(<var>O</var>, <var>P</var>).
</li></ol></emu-alg>
<emu-clause id="ordinarymetadatakeys" aoid="OrdinaryMetadataKeys">
<h1><span class="secnum">3.1.6.1</span>OrdinaryMetadataKeys ( O, P )</h1>
<p>When the abstract operation OrdinaryMetadataKeys is called with Object <var>O</var> and property key <var>P</var> the following steps are taken:</p>
<emu-alg><ol><li>Assert: <var>P</var> is <emu-val>undefined</emu-val> or <emu-xref aoid="IsPropertyKey" id="_ref_25"><a href="https://tc39.github.io/ecma262/#sec-ispropertykey">IsPropertyKey</a></emu-xref>(<var>P</var>) is <emu-val>true</emu-val>.</li><li>Let <var>ownKeys</var> be ? <emu-xref aoid="OrdinaryOwnMetadataKeys" id="_ref_26"><a href="#ordinaryownmetadatakeys">OrdinaryOwnMetadataKeys</a></emu-xref>(<var>O</var>, <var>P</var>).</li><li>Let <var>parent</var> be ? <var>O</var>.[[GetPrototypeOf]]().</li><li>If <var>parent</var> is <emu-val>null</emu-val>, then return <var>ownKeys</var>.</li><li>Let <var>parentKeys</var> be ? <var>O</var>.[[OrdinaryMetadataKeys]](<var>P</var>).</li><li>Let <var>ownKeysLen</var> = ? <emu-xref aoid="Get" id="_ref_27"><a href="https://tc39.github.io/ecma262/#sec-get-o-p">Get</a></emu-xref>(<var>ownKeys</var>, "length").</li><li>If <var>ownKeysLen</var> is <emu-val>0</emu-val>, return <var>parentKeys</var>.</li><li>Let <var>parentKeysLen</var> = ? <emu-xref aoid="Get" id="_ref_28"><a href="https://tc39.github.io/ecma262/#sec-get-o-p">Get</a></emu-xref>(<var>parentKeys</var>, "length").</li><li>If <var>parentKeysLen</var> is <emu-val>0</emu-val>, return <var>ownKeys</var>.</li><li>Let <var>set</var> be a newly created <emu-val>Set</emu-val> object.</li><li>Let <var>keys</var> be ? <emu-xref aoid="ArrayCreate" id="_ref_29"><a href="https://tc39.github.io/ecma262/#sec-arraycreate">ArrayCreate</a></emu-xref>(0).</li><li>Let <var>k</var> be <emu-val>0</emu-val>.</li><li>For each element <var>key</var> of <var>ownKeys</var><ol><li>Let <var>hasKey</var> be ? <emu-xref aoid="Invoke" id="_ref_30"><a href="https://tc39.github.io/ecma262/#sec-invoke">Invoke</a></emu-xref>(<var>set</var>, <code>"has"</code>, <var>key</var>).</li><li>If <var>hasKey</var> is <emu-val>false</emu-val>, then<ol><li>Let <var>Pk</var> be ! <emu-xref aoid="ToString" id="_ref_31"><a href="https://tc39.github.io/ecma262/#sec-tostring">ToString</a></emu-xref>(<var>k</var>).</li><li>Perform ? <emu-xref aoid="Invoke" id="_ref_32"><a href="https://tc39.github.io/ecma262/#sec-invoke">Invoke</a></emu-xref>(<var>set</var>, "add", <var>key</var>).</li><li>Let <var>defineStatus</var> be <emu-xref aoid="CreateDataProperty" id="_ref_33"><a href="https://tc39.github.io/ecma262/#sec-createdataproperty">CreateDataProperty</a></emu-xref>(<var>keys</var>, <var>Pk</var>, <var>key</var>).</li><li>Assert: <var>defineStatus</var> is <emu-val>true</emu-val>.</li><li>Increase <var>k</var> by <emu-val>1</emu-val>.</li></ol></li></ol></li><li>For each element <var>key</var> of <var>parentKeys</var><ol><li>Let <var>hasKey</var> be ? <emu-xref aoid="Invoke" id="_ref_34"><a href="https://tc39.github.io/ecma262/#sec-invoke">Invoke</a></emu-xref>(<var>set</var>, <code>"has"</code>, <var>key</var>).</li><li>If <var>hasKey</var> is <emu-val>false</emu-val>, then<ol><li>Let <var>Pk</var> be ! <emu-xref aoid="ToString" id="_ref_35"><a href="https://tc39.github.io/ecma262/#sec-tostring">ToString</a></emu-xref>(<var>k</var>).</li><li>Perform ? <emu-xref aoid="Invoke" id="_ref_36"><a href="https://tc39.github.io/ecma262/#sec-invoke">Invoke</a></emu-xref>(<var>set</var>, <code>"add"</code>, <var>key</var>).</li><li>Let <var>defineStatus</var> be <emu-xref aoid="CreateDataProperty" id="_ref_37"><a href="https://tc39.github.io/ecma262/#sec-createdataproperty">CreateDataProperty</a></emu-xref>(<var>keys</var>, <var>Pk</var>, <var>key</var>).</li><li>Assert: <var>defineStatus</var> is <emu-val>true</emu-val>.</li><li>Increase <var>k</var> by <emu-val>1</emu-val>.</li></ol></li></ol></li><li>Perform ? <emu-xref aoid="Set" id="_ref_38"><a href="https://tc39.github.io/ecma262/#sec-set-o-p-v-throw">Set</a></emu-xref>(<var>keys</var>, <code>"length"</code>, <var>k</var>).</li><li>return <var>keys</var>.
</li></ol></emu-alg>
</emu-clause>
</emu-clause>
<emu-clause id="ordinary-object-internal-methods-and-internal-slots-ownmetadatakeys">
<h1><span class="secnum">3.1.7</span>[[OwnMetadataKeys]] ( P )</h1>
<p>When the [[OwnMetadataKeys]] internal method of <var>O</var> is called with property key <var>P</var> the following steps are taken:</p>
<emu-alg><ol><li>Return <emu-xref aoid="OrdinaryOwnMetadataKeys" id="_ref_39"><a href="#ordinaryownmetadatakeys">OrdinaryOwnMetadataKeys</a></emu-xref>(<var>O</var>, <var>P</var>).
</li></ol></emu-alg>
<emu-clause id="ordinaryownmetadatakeys" aoid="OrdinaryOwnMetadataKeys">
<h1><span class="secnum">3.1.7.1</span>OrdinaryOwnMetadataKeys ( O, P )</h1>
<p>When the abstract operation OrdinaryOwnMetadataKeys is called with Object <var>O</var> and property key <var>P</var> the following steps are taken:</p>
<emu-alg><ol><li>Assert: <var>P</var> is <emu-val>undefined</emu-val> or <emu-xref aoid="IsPropertyKey" id="_ref_40"><a href="https://tc39.github.io/ecma262/#sec-ispropertykey">IsPropertyKey</a></emu-xref>(<var>P</var>) is <emu-val>true</emu-val>.</li><li>Let <var>keys</var> be ? <emu-xref aoid="ArrayCreate" id="_ref_41"><a href="https://tc39.github.io/ecma262/#sec-arraycreate">ArrayCreate</a></emu-xref>(0).</li><li>Let <var>metadataMap</var> be ? <emu-xref aoid="GetOrCreateMetadataMap" id="_ref_42"><a href="#getorcreatemetadatamap">GetOrCreateMetadataMap</a></emu-xref>(<var>O</var>, <var>P</var>, <emu-val>false</emu-val>).</li><li>If <var>metadataMap</var> is <emu-val>undefined</emu-val>, return <var>keys</var>.</li><li>Let <var>keysObj</var> be ? <emu-xref aoid="Invoke" id="_ref_43"><a href="https://tc39.github.io/ecma262/#sec-invoke">Invoke</a></emu-xref>(<var>metadataMap</var>, <code>"keys"</code>).</li><li>Let <var>iterator</var> be ? <emu-xref aoid="GetIterator" id="_ref_44"><a href="https://tc39.github.io/ecma262/#sec-getiterator">GetIterator</a></emu-xref>(<var>keysObj</var>).</li><li>Let <var>k</var> be <emu-val>0</emu-val>.</li><li>Repeat<ol><li>Let <var>Pk</var> be ! <emu-xref aoid="ToString" id="_ref_45"><a href="https://tc39.github.io/ecma262/#sec-tostring">ToString</a></emu-xref>(<var>k</var>).</li><li>Let <var>next</var> be ? <emu-xref aoid="IteratorStep" id="_ref_46"><a href="https://tc39.github.io/ecma262/#sec-iteratorstep">IteratorStep</a></emu-xref>(<var>iterator</var>).</li><li>If <var>next</var> is <emu-val>false</emu-val>, then<ol><li>Let <var>setStatus</var> be ? <emu-xref aoid="Set" id="_ref_47"><a href="https://tc39.github.io/ecma262/#sec-set-o-p-v-throw">Set</a></emu-xref>(<var>keys</var>, <code>"length"</code>, <var>k</var>, <var>true</var>).</li><li>Assert: <var>setStatus</var> is <emu-val>true</emu-val>.</li><li>Return <var>keys</var>.</li></ol></li><li>Let <var>nextValue</var> be ? <emu-xref aoid="IteratorValue" id="_ref_48"><a href="https://tc39.github.io/ecma262/#sec-iteratorvalue">IteratorValue</a></emu-xref>(<var>next</var>).</li><li>Let <var>defineStatus</var> be <emu-xref aoid="CreateDataPropertyOrThrow" id="_ref_49"><a href="https://tc39.github.io/ecma262/#sec-createdatapropertyorthrow">CreateDataPropertyOrThrow</a></emu-xref>(<var>keys</var>, <var>Pk</var>, <var>nextValue</var>).</li><li>If <var>defineStatus</var> is an <emu-xref href="#sec-completion-record-specification-type"><a href="https://tc39.github.io/ecma262/#sec-completion-record-specification-type">abrupt completion</a></emu-xref>, return ? <emu-xref aoid="IteratorClose" id="_ref_50"><a href="https://tc39.github.io/ecma262/#sec-iteratorclose">IteratorClose</a></emu-xref>(<var>iterator</var>, <var>defineStatus</var>).</li><li>Increase <var>k</var> by <emu-val>1</emu-val>.
</li></ol></li></ol></emu-alg>
</emu-clause>
</emu-clause>
<emu-clause id="ordinary-object-internal-methods-and-internal-slots-deletemetadata">
<h1><span class="secnum">3.1.8</span>[[DeleteMetadata]]( MetadataKey, P )</h1>
<p>When the [[DeleteMetadata]] internal method of <var>O</var> is called with <emu-xref href="#sec-ecmascript-language-types"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">ECMAScript language value</a></emu-xref> <var>MetadataKey</var> and property key <var>P</var> the following steps are taken:</p>
<emu-alg><ol><li>Assert: <var>P</var> is <emu-val>undefined</emu-val> or <emu-xref aoid="IsPropertyKey" id="_ref_51"><a href="https://tc39.github.io/ecma262/#sec-ispropertykey">IsPropertyKey</a></emu-xref>(<var>P</var>) is <emu-val>true</emu-val>.</li><li>Let <var>metadataMap</var> be ? <emu-xref aoid="GetOrCreateMetadataMap" id="_ref_52"><a href="#getorcreatemetadatamap">GetOrCreateMetadataMap</a></emu-xref>(<var>O</var>, <var>P</var>, <emu-val>false</emu-val>).</li><li>If <var>metadataMap</var> is <emu-val>undefined</emu-val>, return <emu-val>false</emu-val>.</li><li>Return ? <emu-xref aoid="Invoke" id="_ref_53"><a href="https://tc39.github.io/ecma262/#sec-invoke">Invoke</a></emu-xref>(<var>metadataMap</var>, <code>"delete"</code>, <var>MetadataKey</var>).
</li></ol></emu-alg>
</emu-clause>
</emu-clause>
</emu-clause>
<emu-clause id="reflection">
<h1><span class="secnum">4</span>Reflection</h1>
<emu-clause id="reflect">
<h1><span class="secnum">4.1</span>The Reflect Object</h1>
<p>This section contains amendments to the Reflect object.</p>
<emu-clause id="reflect-metadatadecoratorfunctions">
<h1><span class="secnum">4.1.1</span>Metadata Decorator Functions</h1>
<p>A metadata decorator function is an anonymous built-in function that has [[MetadataKey]] and [[MetadataValue]] internal slots.</p>
<p>When a metadata decorator function <var>F</var> is called with arguments <var>target</var> and <var>key</var>, the following steps are taken:</p>
<emu-alg><ol><li>Assert: <var>F</var> has a [[MetadataKey]] internal slot whose value is an <emu-xref href="#sec-ecmascript-language-types"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">ECMAScript language value</a></emu-xref>, or <emu-val>undefined</emu-val>.</li><li>Assert: <var>F</var> has a [[MetadataValue]] internal slot whose value is an <emu-xref href="#sec-ecmascript-language-types"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">ECMAScript language value</a></emu-xref>, or <emu-val>undefined</emu-val>.</li><li>If <emu-xref aoid="Type" id="_ref_54"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-data-types-and-values">Type</a></emu-xref>(<var>target</var>) is not Object, throw a <emu-val>TypeError</emu-val> exception.</li><li>If <var>key</var> is not <emu-val>undefined</emu-val> and <emu-xref aoid="IsPropertyKey" id="_ref_55"><a href="https://tc39.github.io/ecma262/#sec-ispropertykey">IsPropertyKey</a></emu-xref>(<var>key</var>) is <emu-val>false</emu-val>, throw a <emu-val>TypeError</emu-val> exception.</li><li>Let <var>metadataKey</var> be the value of <var>F</var>'s [[MetadataKey]] internal slot.</li><li>Let <var>metadataValue</var> be the value of <var>F</var>'s [[MetadataValue]] internal slot.</li><li>Perform ? <var>target</var>.[[DefineMetadata]](<var>metadataKey</var>, <var>metadataValue</var>, <var>target</var>, <var>key</var>).</li><li>Return <emu-val>undefined</emu-val>.
</li></ol></emu-alg>
</emu-clause>
<emu-clause id="reflect.metadata">
<h1><span class="secnum">4.1.2</span>Reflect.metadata ( metadataKey, metadataValue )</h1>
<p>When the <code>metadata</code> function is called with arguments <var>metadataKey</var> and <var>metadataValue</var>, the following steps are taken:</p>
<emu-alg><ol><li>Let <var>decorator</var> be a new built-in function object as defined in Metadata Decorator Functions.</li><li>Set the [[MetadataKey]] internal slot of <var>decorator</var> to <var>metadataKey</var>.</li><li>Set the [[MetadataValue]] internal slot of <var>decorator</var> to <var>metadataValue</var>.</li><li>Return <var>decorator</var>.
</li></ol></emu-alg>
</emu-clause>
<emu-clause id="reflect.definemetadata">
<h1><span class="secnum">4.1.3</span>Reflect.defineMetadata ( metadataKey, metadataValue, target [, propertyKey] )</h1>
<p>When the <code>defineMetadata</code> function is called with arguments <var>metadataKey</var>, <var>metadataValue</var>, <var>target</var>, and <var>propertyKey</var>, the following steps are taken:</p>
<emu-alg><ol><li>If <emu-xref aoid="Type" id="_ref_56"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-data-types-and-values">Type</a></emu-xref>(<var>target</var>) is not Object, throw a <emu-val>TypeError</emu-val> exception.</li><li>Return ? <var>target</var>.[[DefineMetadata]](<var>metadataKey</var>, <var>metadataValue</var>, <var>propertyKey</var>).
</li></ol></emu-alg>
</emu-clause>
<emu-clause id="reflect.hasmetadata">
<h1><span class="secnum">4.1.4</span>Reflect.hasMetadata ( metadataKey, target [, propertyKey] )</h1>
<p>When the <code>hasMetadata</code> function is called with arguments <var>metadataKey</var>, <var>target</var>, and <var>propertyKey</var>, the following steps are taken:</p>
<emu-alg><ol><li>If <emu-xref aoid="Type" id="_ref_57"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-data-types-and-values">Type</a></emu-xref>(<var>target</var>) is not Object, throw a <emu-val>TypeError</emu-val> exception.</li><li>Return ? <var>target</var>.[[HasMetadata]](<var>metadataKey</var>, <var>propertyKey</var>).
</li></ol></emu-alg>
</emu-clause>
<emu-clause id="reflect.hasownmetadata">
<h1><span class="secnum">4.1.5</span>Reflect.hasOwnMetadata ( metadataKey, target [, propertyKey] )</h1>
<p>When the <code>hasOwnMetadata</code> function is called with arguments <var>metadataKey</var>, <var>target</var>, and <var>propertyKey</var>, the following steps are taken:</p>
<emu-alg><ol><li>If <emu-xref aoid="Type" id="_ref_58"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-data-types-and-values">Type</a></emu-xref>(<var>target</var>) is not Object, throw a <emu-val>TypeError</emu-val> exception.</li><li>Return ? <var>target</var>.[[HasOwn]](<var>metadataKey</var>, <var>propertyKey</var>).
</li></ol></emu-alg>
</emu-clause>
<emu-clause id="reflect.getmetadata">
<h1><span class="secnum">4.1.6</span>Reflect.getMetadata ( metadataKey, target [, propertyKey] )</h1>
<p>When the <code>getMetadata</code> function is called with arguments <var>metadataKey</var>, <var>target</var>, and <var>propertyKey</var>, the following steps are taken:</p>
<emu-alg><ol><li>If <emu-xref aoid="Type" id="_ref_59"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-data-types-and-values">Type</a></emu-xref>(<var>target</var>) is not Object, throw a <emu-val>TypeError</emu-val> exception.</li><li>Return ? <var>target</var>.[[GetMetadata]](<var>metadataKey</var>, <var>propertyKey</var>).
</li></ol></emu-alg>
</emu-clause>
<emu-clause id="reflect.getownmetadata">
<h1><span class="secnum">4.1.7</span>Reflect.getOwnMetadata ( metadataKey, target [, propertyKey] )</h1>
<p>When the <code>getOwnMetadata</code> function is called with arguments <var>metadataKey</var>, <var>target</var>, and <var>propertyKey</var>, the following steps are taken:</p>
<emu-alg><ol><li>If <emu-xref aoid="Type" id="_ref_60"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-data-types-and-values">Type</a></emu-xref>(<var>target</var>) is not Object, throw a <emu-val>TypeError</emu-val> exception.</li><li>Return ? <var>target</var>.[[GetOwnMetadata]](<var>metadataKey</var>, <var>propertyKey</var>).
</li></ol></emu-alg>
</emu-clause>
<emu-clause id="reflect.getmetadatakeys">
<h1><span class="secnum">4.1.8</span>Reflect.getMetadataKeys ( target [, propertyKey] )</h1>
<p>When the <code>getMetadataKeys</code> function is called with arguments <var>target</var> and <var>propertyKey</var>, the following steps are taken:</p>
<emu-alg><ol><li>If <emu-xref aoid="Type" id="_ref_61"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-data-types-and-values">Type</a></emu-xref>(<var>target</var>) is not Object, throw a <emu-val>TypeError</emu-val> exception.</li><li>Return ? <var>target</var>.[[GetMetadataKeys]](<var>propertyKey</var>).
</li></ol></emu-alg>
</emu-clause>
<emu-clause id="reflect.getownmetadatakeys">
<h1><span class="secnum">4.1.9</span>Reflect.getOwnMetadataKeys ( target [, propertyKey] )</h1>
<p>When the <code>getOwnMetadataKeys</code> function is called with arguments <var>target</var> and <var>propertyKey</var>, the following steps are taken:</p>
<emu-alg><ol><li>If <emu-xref aoid="Type" id="_ref_62"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-data-types-and-values">Type</a></emu-xref>(<var>target</var>) is not Object, throw a <emu-val>TypeError</emu-val> exception.</li><li>Return ? <var>target</var>.[[GetOwnMetadataKeys]](<var>propertyKey</var>).
</li></ol></emu-alg>
</emu-clause>
<emu-clause id="reflect.deletemetadata">
<h1><span class="secnum">4.1.10</span>Reflect.deleteMetadata ( metadataKey, target [, propertyKey] )</h1>
<p>When the <code>deleteMetadata</code> function is called with arguments <var>metadataKey</var>, <var>target</var>, and <var>propertyKey</var>, the following steps are taken:</p>
<emu-alg><ol><li>If <emu-xref aoid="Type" id="_ref_63"><a href="https://tc39.github.io/ecma262/#sec-ecmascript-data-types-and-values">Type</a></emu-xref>(<var>target</var>) is not Object, throw a <emu-val>TypeError</emu-val> exception.</li><li>Return ? <var>target</var>.[[DeleteMetadata]](<var>metadataKey</var>, <var>propertyKey</var>).
</li></ol></emu-alg>
</emu-clause>
</emu-clause>
</emu-clause></div></body>